Carburetor



y 9 19340 G. E. ERICSON 1,967,708

CARBURETOR Filed Jan. 16, 1931 5 Sheets-Sheet 1 550,245 Hie/550MINVENTOR ATTORNEY 6. E. ERICSON July E934 CARBURETOR Filed Jan. 16,1.951 5 Sheets-Sheet 2 INVENTOR ATTORNEY J y 24, 1934- G. E. ERIICSONmazms CARBURETOR Filed Jan. 16, 1951 5 Sheets-Sheet 4 Gfiafi E i /650MBNVENTOR I 1 ATTORNEY G. E. ERICSON July 24, 1934.

CARBURETOR Filed Jan. 16, 1951 5 Sheets-Sheet 5 fl 1; v

650265 E ERIC-501V 11v VENTOR A TTRNEY Patented July 24, 1934 UNITEDSTATES PATENT OFFICE CARBURETOR Application January 16, 1931, Serial No.509,105

8 Claims.

This invention relates to carburetors and more particularly to downdraftcarburetors for internal combustion engines in which the fuel for highand low speed operation is discharged 6 through separate nozzles. In theplain tube type of carburetor, the fuel for low speed operation isordinarily supplied through an idle" passageway which discharges intothe mixing conduit at a point near the edge of the but- 10 terfiythrottle valve when it is in closed or nearly closed position. The fuelfor high speed operation is ordinarily supplied through a main nozzlewhich discharges in the central part of the mixing conduit at a pointanterior to the throttle valve.

It is common practice to connect the idle and the main nozzle to eachother and then through a common supply passage to the source of fuelsupply, and a metering orifice or passageway of 2 calibrated capacity isusually located in the common connection. The reason for this is that itis not desirable to have the main fuel nozzle begin to discharge fueluntil a fairly rapid rate of air flow through the mixing conduit hasbeen attained. If the main nozzle were permitted to discharge fuel withthe throttle in fully closed position, the fuel would come offirregularly in slugs which would not be vaporized on account of the slowair speed.

Even with this arrangement many difficulties are encountered, for thesuction which is built up by the idling conduit tends to withdraw thefuel from the main nozzle so that it contains nothing but air, and ifthe throttle is suddenly opened, a large amount of air can pass throughthe mixing conduit of the carburetor while the main nozzle is drawing inenough fuel to fill it to the point where it will begin discharging.This condition causes a lag in the acceleration of the motor which mustbe corrected by a pump, and places an undue burden on the pump which, inturn, gives rise to serious difficulties due to changing temperature.

It will be understood that when the throttle is suddenly opened, theabsolute pressure in the intake manifold of the engine is greatlyincreased, causing condensation of fuel on the walls of the manifold anda corresponding momentary reduction in the fuel content of the mixtureflowing into the engine. A correction for this is ordinarily made by theprovision of an accelerating pump, but this is not an ideal solution,for the pump discharges in proportion to the movement of the throttleand not in' proportion to the amount of air flowing through condition.

the carburetor. It is accordingly desirable to keep the pump as small aspossible and to avoid placing extra burden on it.

Another difliculty in the operation of downdraft curburetors of the typeshown in this application relates to what is known as percolation.Gasoline as ordinarily sold at the present time is a mixture of a numberof diiferent hydrocarbons having boiling points ranging from slightlyabove 100 degrees Fahrenheit to nearly 400 degrees Fahrenheit. Where asmall amount of the fuel is contained in the passageways of thecarburetor and where the carburetor is subjected to high temperatures asin the case of the downdraft carburetor shown herein, the constituentshaving lower boiling points tend to form small bubbles in the upwardlyextending passageways such as the nozzle and as these bubbles rise inthe nozzle they tend to create a flow of fuel out of the nozzle and intothe carburetor mixing passages even when the engine is not in operation.This difliculty is especially apparent when the engine is operated insuch a manner as to bring it to a high temperature and then stopped fora few minutes. Percolation of this character is frequently suflicient tocompletely empty the contents of the bowl or float chamber into theintake manifold of the engine, causing an almost impossible starting Itis an object of this invention to produce a carburetor in which thedischarge of the main nozzle may be delayed until the air speed throughthe mixing conduit has been increased to such an extent that the fueldischarged from 99 the main nozzle will be properly vaporized under allconditions.

It is a further object of this invention to produce a carburetor of theabove described type in which the main nozzle will not be emptied offuel during the operation of the idle tube, whereby the main nozzle maybegin to discharge instantly when the throttle is opened.

It is a further object of this invention to produce a carburetor inwhich the main nozzle and 100 the idle tube are supplied throughseparate calibrated passageways so that each may be controlled oradjusted without affecting the other.

It is a further object of this invention to produce a carburetor inwhich the flow of fuel from the float chamber to the main nozzle is cutoil whenever the engine is not in operation, so that the emptying of thebowl or float chamber into the mixing conduit by percolation thru themain nozzle will be prevented.

Other objects of.the invention will appear from the followingdescription and the accompanying drawings, referring to which:

Figure 1 is a vertical sectional view of a downdraft carburetorembodying oneform of my invention, the section being taken along theline 1-1 of Figure 2.

Figure 2 is a plan view of the carburetor shown in Figure 1.

Figure 3 is a side elevation of the carburetor shown in Figure 1, withparts in section for better illustration thereof, the section beingtaken along the line 3-3 of Figure 2.

Figure 4 is a side elevation of the carburetor shown in Figures 1 to 3with parts in section, the section being taken along the line 4-4.

Figure 5 is a side elevation of the adjustable coupling for the meteringrod, with parts shown in section for better illustration thereof.

Figure 6 is a diagrammatic view of the device.

The reference numeral 1 indicates a lower casting forming the main bodymember of the carburetor. This casting is provided with a flange 2 bymeans of which it may be attached to the intake manifold '70 of aninternal combustion engine. An upper casting 3 is attached to the upperend of the body member 1 and forms an air inlet or air horn. A downdraftmixing conduit 4 having its inlet end in the upper end of the air hornand its outlet in the flange 2 is formed in the carburetor; the lowerpart of the mixing conduit, as indicated at 5, may be considered themain mixing chamber of the carburetor. A choke valve 6 is provided forcontrolling the admission of air through the air horn, and a throttlevalve '7 is provided to control the rate of discharge of the air andfuel mixture to the engine.

In this embodiment of the invention, a nest of three venturis is usedcomprising a primary venturi 8, a secondary venturi 9, and a mainventuri 10. Each of the first two venturis discharges at a pointadjacent the throat of the next larger venturi. The lower casting 1 hasa float chamber 11 made integral therewith, and fuel is supplied to thefloat chamber through a connection 12 from any suitable source. A valve13 controlled by a fioat 14 controls the admission of fuel to the floatchamber and maintains the height of the fuel substantially at the levelshown in Figure 4. This level is also indicated by the broken line A-Ain Figure 3.

The fuel for the low speed operation of the carburetor is suppliedthrough a passageway 15 which receives the fuel below the fuel level inthe float chamber 11 and is connected to a metering orifice 16 in across passageway 17 which leads to the downwardly extending idle passage18 from which the fuel is discharged at the edge of the'throttle valve'7 through an elongated port 19. An adjusting screw 20 controlling theadmission of air at the upper part of the idle passage 18 is provided toprevent syphoning of the fuel when the carburetor is not in operation.The air for this purpose is admitted to the port 21 and adjusted by thetapered end of the screw 20 which acts as a valve. It will be obviousthat the fuel supply for low speed operation can be fully controlled bysuitably calibrating the capacity of the restriction 16 and the shape,size, and position of the port 19, and the adjustment of the screw 20.

The fuel for high speed operation is supplied through a nozzle 22 whichis connected by means of the passageways 23 to the fuel chamber. Ametering plug 24 is mounted-in the inlet end of the passageways 23 andhas a calibrated passageway extending therethrough to control theadmission of fuel to the main nozzle. A metering rod 25 provided withone or more steps 26 of different diameter extends into the meteringplug 24, and a valve portion 2'7 is formed on the metering rod justabove the steps 26 so that when the rod is pushed all-the way in -to themetering plug, the flow of fuel will be entirely out off, as indicatedin Figure 4. The position of the metering rod is controlled by theposition of the throttle in the following manner:

The throttle shaft 28 is provided with a' crank 29 which is connected bymeans of a link 30 to the crank 31 on the rock shaft 32 which is mountedon a pillow block 33 on the member 34 which forms the cover of the floatchamber of the carburetor. The crank 31 is provided with a clip 35carrying a pintle or crank pin 36 which is pivotally engaged with theupper end of the tube 37, as shown in Figures 1 and 4. The lower end ofthe tube is turned in to slidably fit the metering rod 25, and the upperend of the metering rod is headed, as indicated at 38. A spring 39 isplaced in the tube 37 between the pin 36 and the head of the meteringrod so that the rock shaft 32 and throttle shaft 28 may have a continuedmovement after the valve 27 has come in contact with the metering plug24.

It will be noted that the rock shaft 32 is pro vided with a crank 40connected by means of a link 41 to the rod 42 which operates the piston43 in the cylinder 44. These parts belong to the accelerating pump ofthe carburetor and form no part of this invention. It will be understoodthat my invention is to be applied to carburetors, irrespective ofwhether they are equipped with an accelerating pump or not, and that oneof the objects of the invention is to make it possible to use a smalleraccelerating pump, or, in some cases, to eliminate it altogether. Forthe purpose of this specification, it will sufficient to say that on theup-stroke of the piston 43, fuel is withdrawn from the float chamber 11and on the down-stroke of the piston 43, fuel is discharged through anozzle 48 to the mixing conduit of the carburetor.

The operation of the device is as follows:

When the throttle is in the position shown in Figure 3, the suction onthe outlet side of the throttle valve will draw air and fuel through theport 19 to supply the needs of the engine, and as the throttle valve isgradually opened, this fuel supply is continued until the throttle valvehas moved far enough from the port 19 to partially relieve the suctionat that point or at least to relieve it to such an extent that the airflowing through the passageway 21 will kill the suction in the idle tube18 to such a point that it will no longer pull liquid fuel up to thelevel of the cross air passage 1'7. It will be obvious that the idletube will discontinue its operation gradually and not abruptly duringgradual opening movements of the throttle.

As the throttle is opened, the throttle shaft 28 turns in a clockwisedirection (with reference to Figure 1) pushing the link 30 upwardly androcking the shaft 32 in a clockwise direction. During the first stagesof the opening movement of the throttle, the spring 39 retains the valve27 on its seat, preventing the discharge of fuel from the nozzle 22, butas the opening movement is continued, the valve 27 is gradually liftedoff its seat and the nomle 22 comes into operation. The nozzle is alwaysfilled with fuel, because there is no way of getting it empty, and evenif an air bleed to the nozzle is provided, there will generally besumcient leakage at the valve 27 to keep the nozzle full.

After the valve 27 has started to open, a very slight further movementof the throttle will bring it to fully open position. It will beunderstood, however, that the extent of throttle movement necessary tofully open the valve 27 can be made to depend upon the taper of thevalve 27, the diameter of the valve, and the length of thecranks 29 and31. The carburetor will be so calibrated by adjustment of these variouselements that the main nozzle will begin to discharge fuel in the sameratio as the idle ceases to discharge.

In case an adjustment is desired for the position of the valve 27, themetering rod and operating means therefor may be formed in the mannershown in Figure 5. The tube 45 is substituted for the tube 37 in theother figures. The tube 45 is threaded at its lower end and providedwith a cap member 46 which may be adjusted up or down on the tube andheld in place by a lock nut 47. The-spring 39 may be the same as used inthe device shown in Figure 4, and the metering rod may also be the same.It is obvious that many other forms of adjustment will suggestthemselves to a mechanic skilled in the art.

I claim:

1. In a downdraft carburetor of the plain tube type, means forming adowndraft mixing conduit, a throttle valve near the lower end of saidconduit controlling the flow of mixture therethrough, a plurality ofcoaxial venturis in said conduit above said throttle valve, meansforming a main fuel supply chamber, a main fuel supply nozzle leadingfrom said fuel supply chamber and discharging into the inner of saidventuris, a valve for controlling the flow of fuel through said nozzle,said valve being adapted to entirely cut off the flow of fuel throughsaid nozzle in one operated position thereof, said valve beingoperatively connected to said throttle and being moved to fully closedposition by a closing movement of said throttle.

2. In a downdraft carburetor of the plain tube type, means forming adowndraft mixing conduit, a throttle valve near the lower end of saidconduit controlling the flow of mixture therethrough, a plurality ofcoaxial venturis in said conduit above said throttle valve, meansforming a main fuel supply chamber, a main fuel supply nozzle leadingfrom said fuel supply chamber and discharging into the inner of saidventuris, a valve for controlling the fiow of fuel through said nozzle,said valve being adapted to entirely cut off the flow of fuel throughsaid nozzle in one operating position thereof, said valve beingoperatively connected to said throttle and being moved to fully closedposition by a closing movement of said throttle, said valve being movedinto fully closed position before the throttle valve reaches fullyclosed position, and resilient means in the connection between saidthrottle and said valve for permitting the throttle to continue itsclosing movement after said valve is entirely closed.

3. In a carburetor, means forming a mixing conduit, a throttle valvecontrolling the flow of mixture therethrough, a fuel nozzle fordischarging fuel into said conduit, a metering device for controllingthe admission of fuel to said nozzle, said metering device comprisingmeans forming a calibrated passageway, a metering rod having a portionof smaller diameter than saidpassageway normally extending therein, avalve portion on said metering rod of larger diameter than saidpassageway, a connection between said throttle valve and said valve,said connection closing said valve before said throttle reaches closedposition, and said connection comprising a yieldable member and adaptedto be compressed after said valve has been closed to permit thecompletion of the closing movement of the throttle.

4. In a carburetor, means forming a mixing conduit, a throttlecontrolling the passage of mixture through said conduit, a single meansfor supplying fuel to said carburetor during low speed operationcomprising a passageway discharging adjacent the edge of said throttle,a single means supplying all of the fuel required for said carburetorfor constant speed operation while said throttle is in open positioncomprising a main fuel nozzle discharging anterior to said throttle, anda valve for cutting off one of said fuel supply means as the other ofsaid fuel supply means goes into operation.

5. In a plain tube downdraft carburetor, means forming a downdraftmixing conduit, a throttle valve controlling the flow of mixture throughsaid conduit, means forming a fuel supply chamher, an idle passage inthe general form of an inverted U receiving fuel from said supplychamber and discharging adjacent the edge of said throttle, saidthrottle being located below the level of fuel in said supply chamber,an air bleed in said idle passage above the level of fuel in said supplychamber, a venturi in said conduit having its throat slightly above thelevel of the fuel in said supply chamber, said venturi dischargingdownwardly and terminating below the level of the fuel in said supplychamber, a main fuel nozzle connected to said supply chamberindependently of said idling passage and discharging near the throat ofsaid venturi,

said idling passage and said main nozzle forming respectively the solemeans for supplying fuel to said carburetor at constant low speedoperation and constant high speed, and a valve operated by said throttlefor controlling the flow through one of said fuel supply means, saidvalve being adapted to prevent the simultaneous operation of said supplymeans. I

6. In a carbureteor of the plain tube type,

means forming a mixing conduit, a throttle controlling the passage ofmixture through said conduit, means forming a constant level fuel supplychamber, a main nozzle connected to said fuel supply chamber anddischarging in said mixing conduit slightly above the level of fuel insaid supply chamber, a venturi surrounding the discharge outlet of saidnozzle, means for supplying fuel to said carburetor for low speedoperation, and means to prevent the discharge of fuel from said mainnozzle until a flow of air through said mixing conduit has been producedof sufficient velocity to vaporize fuel discharging from said mainnozzle.

7. In a downdraft carburetor, means forming a constant level liquid fuelchamber, means forming a downwardly directed mixing conduit, a throttlevalve near the lower end of said conduit, a main fuel nozzle connectedto said fuel chamber at a point below the fuel level' mounted in saidmixing conduit, a main nozzle for conveying fuel from said constantlevel fuel chamber to said mixing conduit, said main nozzle having itsdischarge outlet just slightly above the fuel level of said chamber, avalve for cutting off the flow of fuel from said constant level chamberthru said main nozzle, connections between said throttle and said valvefor closing the throttle when the valve is closed, an idling passagewayleading from said constant level chamber upwardly to a point above thefuel level and then downwardly to a point adjacent the edge of thethrottle when same is in closed position, said idling passage having avent at a point above said fuel level and being supplied with fuel fromsaid constant level fuel chamber independent of said main nozzle.

GEORGE R. ERICSON.

